For decades, researchers have collected television audience information to develop television ratings that are useful to advertisers and broadcasters in evaluating the size and demographics of audiences for particular programming. In order to obtain such information, the researcher identifies a sample of households or individuals selected to represent a defined population. The defined population can be any population under review. For example, local television audiences, national television audiences, households whose incomes fall within a certain range, persons of a particular origin, or other groups may be of interest to the researcher. The researcher uses the information collected from a sample to produce television audience statistics and estimates for the defined population. Television audience information may include, but is not necessarily limited to, television status (on or off), program information, and the identity of the person or persons using the television at a given time period. The television information collected is essential when determining the demographics and the number of television users.
An example of a system utilized to provide some of the foregoing demographic information is described in U.S. Pat. No. 2,924,496, assigned to AC Nielson Company. In this system, a meter must be invasively attached to the television receiver, as well as to any cable converter and VCR attached to the television set. Thus, installation is cumbersome and may cause concern over possible signal interference or damage to the receiver, making the system less palatable to the participating household user than a non-invasive system. The resulting reluctance of households or individuals to participate as members of the sample audience may skew the sample audience demographics.
Furthermore, an invasive system in a house might be disconnected by a member of the household without prompt detection. If detection does not occur in a timely manner, the lack of participation in the sample audience will skew the results of the statistics and estimates based on the sample audience.
To overcome the problems associated with invasive television audience participation measurement systems, non-invasive systems are presently under development or have been developed by companies such as Statistical Research, Inc. of Westfield, N.J. Naturally, an essential element of a non-invasive system would be an external sensor to measure certain television status information, such as on/off condition or program identification information.
One potential problem with such a sensor is that there may be objection to permanent attachment, and non-permanent attachment can lead to inaccurate information. By example, a detached sensor may result in a television off condition signal, when indeed the television is on.
The present invention overcomes the foregoing problems by providing a non-invasive television audience participation measurement system attached to a television, with a means for detecting detachment. Although the present invention is contemplated for use with a television audience participation measurement system, such as a system for determining the on/off condition of a television, the present invention may be used to detect the detachment of any mountable sensor.